Aims: To determine abundance of potential pathogenic microorganisms in pangasius and tilapia farms in five major fish-producing areas in Bangladesh by PCR approaches. Methodology and results: Important microbial water quality indicators were studied in water of 38 fish farms producing pangasius (Pangasianodon hypophthalmus) and tilapia (Oreochromis niloticus) in five major fish-producing areas of Bangladesh. The parameters included physicochemical data and PCR detection of total coliforms and E. coli, species of potentially pathogenic Vibrio, and cyanobacterial genes encoding the toxins microcystin and saxitoxin. Quantitative PCR showed that coliform bacteria occurred in all fish farms with densities from one to 2.2 × 105 per mL, while E. coli ranged from none to 5.0 × 104 per mL. Numbers of total coliforms and E. coli were higher in pangasius farms than in tilapia farms, and when high abundances occurred, coliform bacteria and E. coli bacteria co-varied. Detection of Vibrio-specific genes indicated presence of Vibrio species in 76% of the farms and included V. vulnificus and V. cholerae. The human pathogen type of V. cholerae (carrying the ctxA gene) and the fish pathogen V. parahaemolyticus were not detected. The microcystin-encoding mcyE gene ranged from undetectable to 2.6 × 105 copies per mL and tended to be highest in pangasius farms. The saxitoxin-encoding gene sxtA was not found in any of the farms. Conclusion, significance and impact of study Based on the high abundance of especially coliform bacteria and E. coli, we recommend more efficient water quality monitoring systems to improve detection and control of fecal coliforms and to reduce presence of microcystin-producing cyanobacteria in aquaculture farms in Bangladesh
Water Quality ; Tilapia ; Catfishes

Aims: This study aimed to isolate and characterize putative new probiotic with antimicrobial properties against common fish pathogens from the gut of Oreochromis spp. (red tilapia). Methodology and results: A total of 28 colonies were isolated from gut of Oreochromis spp. and characterized phenotypically. Eight isolates were selected for probiotic characterization. Temperature, salinity, pH and bile salt tolerance, antibiotic susceptibility and antimicrobial test against selected fish pathogens (Aeromonas hydrophila, Edwardsiella tarda and Staphylococcus aureus subsp. aureus ATCC 25923) were conducted. Characterization studies revealed isolates suited for freshwater environment and exhibited tolerance against wide range of salinity, pH and bile salt. Isolates displayed different antibiotic susceptibility profile, with six exhibited antimicrobial properties against E. tarda. Molecular identification based on 16S rRNA gene sequencing showed 99.44%, 98.59% and 91.21% sequence similarity with Leuconostoc pseudomesenteroides strain 3832T, Leuconostoc lactis strain KCC202369T and Leuconostoc mesenteroides strain 4332T, respectively as compared to known sequence in the GenBank. When identified Leuconostoc spp. were coated on feed pellets, no major decrease in viability over 21 days of storage at 4 °C were observed, with an average of 8 log CFU/mL. Conclusion, significance and impact of study The characterized species allow further application assessment of the probiotic-supplemented tilapia feed. Host-originated Leuconostoc displayed potential antimicrobial properties against fish pathogen E. tarda. The isolates Leuconostoc is expected to provide protective effect for Oreochromis spp. against edwardsiellosis and to exert beneficial effects more efficiently as compared to commercial probiotics which are not specifically target for Oreochromis spp., thereby indirectly helping fish farmers in achieving economic sustainability and increase affordability of fish.
Leuconostoc ; Anti-Infective Agents ; Tilapia ; Edwardsiella tarda--pathogenicity ; Probiotics

OBJECTIVE: This paper examines the potential carcinogenic risk to human health associated with arsenic levels in five commercially important fish products from Laguna de Bay.
METHODS: Fish samples were collected in eight sampling stations in three major areas of the lake during the dry and wet seasons.  Coordinates of sampling locations were recorded using Global Positioning System and plotted in Geographic Information System digital maps. Analysis of arsenic was conducted using Atomic Absorption Spectrophotometer.
RESULTS: The highest life time cancer risk for arsenic was computed for tilapia from sampling station 2B during the dry season with risk value of 8.51x10-5 or about 85 excess cancer cases per 1,000,000 populations. Calculated cancer risks showed seasonal variations that were distinct among the five fish species. Excess life time cancer risks associated with fish consumption during dry season showed the following order of magnitude: Tilapia > Bighead carp > Kanduli >Bangus > Dalag. For wet season, the order of magnitude was: Bighead carp > Bangus > Kanduli >Tilapia > Dalag. Correlation analyses showed that fish mean standard size do not have significant effect on the levels of arsenic in fish samples for both dry and wet seasons.
CONCLUSION: This study concludes from the point of view of disease prevention that long-term consumption of five commercially important fish species from Laguna de Bay may cause significant carcinogenic health risk.

Animal ; Lakes ; Seasons ; Arsenic ; Tilapia ; Geographic Information Systems ; Bays ; Spectrophotometry, Atomic ; Fish Products ; Carcinogens ; Neoplasms ; Carps

This study was done to evaluate the effect of Ca source using fish (Tilapia mossambica) scales on the bone metabolism. Male Sprague-Dawley rats, 4 weeks of age, were fed low-calcium diet (0.15% Ca) for 2 weeks. The rats on the low-calcium diet were further assigned to one of following three groups for an additional 4 weeks: 1) Ca-depletion group (LoCa) given 0.15% Ca diet (CaCO3), 2) Ca-repletion group (AdCa) given 0.5% Ca diet (CaCO3), 3) Ca-repletion diet (AdFa) received 0.5% Ca diet (Ca source from Tilapia mossambica scales). Serum parathyroid (PTH) and calcitonin showed no differences among experimental groups. Whereas LoCa group elevated the turnover markers, serum ALP and osteocalcin, and urinary deoxypyridinoline (DPD), AdCa and AdFa groups reduced their values. Elevation in the femoral weight, ash and Ca contents was observed in AdCa and AdFa groups. Bone mineral density was increased in AdCa and AdFa groups by 25-26% compared with LoCa group. These data demonstrate that Ca repletion with either Ca source from Tilapia mossambica scales or CaCO3 is similarly effective in the improvement of bone turnover markers and BMD, suggesting the usefulness of Tilapia mossambica scales in the prevention of bone loss compared with CaCO3.
Amino Acids ; Animals ; Biomarkers ; Bone Density ; Calcitonin ; Calcium ; Diet ; Humans ; Male ; Osteocalcin ; Rats ; Rats, Sprague-Dawley ; Tilapia ; Weights and Measures

Serum immunoglobulins from Israeli carp (I. carp) were purified using affinity chromatography. Fish were immunized with purified mouse IgG, and the specific fish antibodies purified from the immune serum on a mouse IgG-immobilized agarose gel. Rabbit anti-carp Ig (Raclg) antibodies were produced following hyperimmunization with mlgG specific I. Carp Ab. SDS-PAGE analysis under reducing condition showed that I. carp Ig (clg) were composed of two u-like heavy chains with about 82 and 50 kD, respectively and one light chain with about 25 kD. On immunoblotting analysis, however, Raclg failed to react with light chain. When both protein A and protein G purified normal clg were compared with mlgG specific clg, no significant structural differences among them were observed. To investigate if there is any homology between other fish Ig molecules, cross-reactivity of Raclg against Ig molecules from 6 different fish sera and mouse control serum was checked on immunoblotting analysis. As a result, Raclg responded to only carp and tilapia Ig molecules, indicating that both tilapia and carp are very closely associated, especially, in the genetic basis of immunoglobulin structure. In flow cytometry study, Raclg appeared to recognize 45.8% of carp Ig+, 14.5% of catfish Ig+ and <5% of tilapia Ig+ cells. The result suggest the heterogeniety between receptor immunoglobulins on B-like lymphocytes and soluble immunoglobulins in serum. It is crucial to obtain pure fish immunoglobulins to produce reagent antibodies as tools for the study of their specific immune response.
Animals ; Antibodies ; Carps* ; Catfishes ; Chromatography, Affinity ; Electrophoresis, Polyacrylamide Gel ; Flow Cytometry ; Immunoblotting ; Immunoglobulin G ; Immunoglobulins* ; Lymphocytes ; Mice ; Sepharose ; Staphylococcal Protein A ; Tilapia

The objectives of this study were to assess the potential of two photosynthetic bacteria (PSB), Rhodopseudomonas palustris HZ0301 and Rhodobacter sphaeroides HZ0302, as probiotics in aquaculture. The viability of HZ0301 and HZ0302 in simulated gastric transit conditions (pH 2.0, pH 3.0 and pH 4.0 gastric juices) and in simulated small intestinal transit conditions (pH 8.0, with or without 0.3% bile salts) was tested. The effects of HZ0301 and HZ0302 on the viability and permeability of intestinal epithelial cell in primary culture of tilapias, Oreochromis nilotica, were also detected. All the treatments were determined with three replicates. The simulated gastric transit tolerance of HZ0301 and HZ0302 strains was pH-dependent and correspondingly showed lower viability at pH 2.0 after 180 min compared with pH 3.0 and pH 4.0. Both HZ0301 and HZ0302 were tolerant to simulated small intestine transit with or without bile salts in our research. Moreover, there was no significant difference (P>0.05) among three treatments including the control and the groups treated with HZ0301 or HZ0302 both in intestinal epithelial cell viability and membrane permeability, showing no cell damage. In summary, this study demonstrated that HZ0301 and HZ0302 had high capacity of upper gastrointestinal transit tolerance and were relatively safe for intestinal epithelial cells of tilapias.
Animals ; Gastrointestinal Tract ; microbiology ; Microbial Viability ; Phototrophic Processes ; Rhodobacter sphaeroides ; isolation & purification ; physiology ; Rhodopseudomonas ; isolation & purification ; physiology ; Species Specificity ; Tilapia ; microbiology

The behavioral responses of a tilapia (Oreochromis niloticus) school to low (0.13 mg/L), moderate (0.79 mg/L) and high (2.65 mg/L) levels of unionized ammonia (UIA) concentration were monitored using a computer vision system. The swimming activity and geometrical parameters such as location of the gravity center and distribution of the fish school were calculated continuously. These behavioral parameters of tilapia school responded sensitively to moderate and high UIA concentration. Under high UIA concentration the fish activity showed a significant increase (P<0.05), exhibiting an avoidance reaction to high ammonia condition, and then decreased gradually. Under moderate and high UIA concentration the school's vertical location had significantly large fluctuation (P<0.05) with the school moving up to the water surface then down to the bottom of the aquarium alternately and tending to crowd together. After several hours' exposure to high UIA level, the school finally stayed at the aquarium bottom. These observations indicate that alterations in fish behavior under acute stress can provide important information useful in predicting the stress.
Ammonia ; administration & dosage ; Animals ; Artificial Intelligence ; Behavior, Animal ; drug effects ; physiology ; Dose-Response Relationship, Drug ; Exercise Test ; methods ; Image Interpretation, Computer-Assisted ; methods ; Social Behavior ; Swimming ; physiology ; Tilapia ; physiology

To study the function of the GnRH protein, the recombinant pMAL-GnRH was constructed and expressed in TB1 E. coli. The cDNA encoding gonadotropin-releasing hormone (GnRH) and GnRH associated peptide (GAP) was amplified from total RNA of O. aurea pituitary glands by reverse transcription polymerase chain reaction (RT-PCR), and then blasted against other GnRH cDNA sequences in the GenBank. The analysis of the sequence data indicated that the coding region of the cDNA fragment, which encoded 89 amino acid residues, was about 400 bp in size. The amplified cDNA fragment was cloned into the prokaryotic expression vector, pMAL-c2x, to produce the expression vector pMAL-GnRH. The recombinant plasmid was transformed into E. coli TB1. GnRH-MBP fusion protein was obtained after the addition of IPTG into the growth media. SDS-PAGE analysis revealed that the GnRH-MBP was expressed after induction with IPTG for 4 h. A protein band of 56 kD appeared on SDS-PAGE gel and was proved by Western blot. The mass production of the recombinant protein was about 41.6% of total bacteria protein. After purification and cleavage of the fusion protein purified GnRH protein could be obtained. Then the fusion protein was used to immunise some ICR mice to produce anti-GnRH antibody. This fusion protein could significantly elicit specific antibody response in immunized mice compared with the blank groups, and the titers against GnRH reached peak 0.707 +/- 0.320 at the 5th week after immunization. These results demonstrated that recombinant protein could induce high GnRH antibody responses in laboratory animals.
Animals ; Cloning, Molecular ; Escherichia coli ; genetics ; Gonadotropin-Releasing Hormone ; genetics ; immunology ; physiology ; Mice ; Mice, Inbred ICR ; Plasmids ; Recombinant Fusion Proteins ; biosynthesis ; immunology ; isolation & purification ; Reverse Transcriptase Polymerase Chain Reaction ; Tilapia ; physiology